1. Field of the Invention
The present invention relates to an image-drawing device and an image-drawing method, and in particular, to an image-drawing device equipped with image-drawing heads which move relative to an image-drawing surface in a predetermined direction along the image-drawing surface, and to an image-drawing method using the image-drawing heads.
2. Description of the Related Art
Conventionally, as an example of an image-drawing device, various exposure devices have been proposed which carry out image exposure by light beams modulated in accordance with image data, by using spatial light modulators (image-drawing elements) such as digital micromirror device (DMDs) or the like. A DMD is a mirror device in which a large number of micromirrors, at which the angles of the reflecting surfaces thereof are varied in accordance with control signals, are lined-up two-dimensionally in L lines×M columns on a semiconductor substrate formed of silicon or the like. Actual exposure is carried out by scanning a DMD in a given direction along an exposure surface.
Generally, the micromirrors of the DMD are arranged such that the direction in which the respective lines are lined-up and the direction in which the respective columns are lined-up are orthogonal to one another. By disposing such a DMD at an incline with respect to the scanning direction, the intervals between the scan lines at the time of scanning can be made to be closer, and the resolution can be increased. For example, Japanese Patent Application National Publication No. 2001-500628 discloses, in an illumination system which guides light to a subregion (a spatial light modulator) provided with a plurality of light valves, increasing the resolution by setting the sub-region at an incline with respect to the projection on the scan lines. In accordance with this method, the resolution in the direction orthogonal to the scanning direction can be increased. However, with respect to the resolution in the direction orthogonal to the scanning direction, because the spatial light modulator is arranged two-dimensionally, although the resolution can be easily increased by adjusting the numbers of lines and columns and the angle of inclination, the resolution may become higher than needed depending on the case.
On the other hand, the resolution in the scanning direction is usually determined by the scanning speed and the modulating speed of the spatial light modulator. Accordingly, in order to increase the resolution in the scanning direction, either the scanning speed must be made to be slower, or the modulating speed of the spatial light modulator must be made to be faster. However, if the scanning speed is made slower, the image-drawing speed becomes slower, and a problem arises in that produceability deteriorates. Further, there are limits to increasing the modulating speed of the spatial light modulator.